Nutrition, diet and body weight Flashcards
what does metabolism mean
the chemical processes that occur within a living organism in order to maintain life
what are catabolic processes
breaking down molecules to release energy in the form of reducing power
what are anabolic processes
using energy and raw materials to make larger molecules for growth and maintenance
name four pathways that contribute to metabolism
- detoxification (remove toxins)
- oxidative (convert food to energy)
- biosynthetic (produce basic building blocks for cells)
- fuel storage + mobilisation (allow fuel to be mobilised when we are not eating or need increased energy)
what is energy
the capacity to do work
what energy do cells use
cells use chemical bond energy to drive energy-requiring activities
name 5 things all living things require energy for
- biosynthetic work (synthesis of cellular components e.g. making proteins)
- transport work (movement of ions and nutrients across membranes e.g. sodium-potassium pump)
- mechanical work (muscle contraction)
- electrical work (nervous conduction)
- osmotic work (kidney)
what are the three components of ATP
adenosine
ribose sugar
3 phosphate groups (alpha, beta, gamma)
ATP-ADP cycle
Process by which cells regenerate ATP. ADP forms when a phosphate group is removed from ATP, then ATP forms again as ADP gains a phosphate group. Allows the controlled release of energy from ATP in cells
energy usage (ATP to ADP + Pi)
ion transport
muscle contraction
biosynthesis
thermogenesis
detoxification
energy production by oxidation of (ADP + Pi to ATP)
lipids
carbohydrates
protein
alcohol
what is dietary fuel that exceeds body’s immediate energy needs stored as
fat in adipose tissue
glycogen in liver or muscle
stores are mobilised between meals and during periods of starvation and prolonged exercise
what is the units of food energy
kilojoule (kJ)
what is a kcal
amount of energy needed to raise temperature of 1kg of water by 1 degree celsius
1kcal = 4.2kJ
what is an exergonic reaction
when the energy released is greater than the energy input
what is an endergonic reaction
when the energy input is greater than the energy released
7 essential components of a normal healthy diet
carbohydrates
protein
fat
minerals
vitamins
water
fibre
what are the macronutrients
carbohydrates, proteins, and fats
what are the micronutrients
minerals and vitamins
why is fibre important in our diet
necessary for normal GI function
binds to bile salts and passes out through faeces
lowers cholesterol
what is energy balance
to maintain our body weight we must stay in energy balance i.e. the energy in the food we eat must match our energy consumption over time
four forms of carbohydrates
monosaccharides - single sugar units
disaccharides - 2 sugar units
oligosaccharides - 3-12 sugar units
polysaccharides - 10-1000s sugar units
name the 7 major dietary carbohydrates
starch
sucrose
lactose
fructose
glucose
maltose
glycogen
9 essential amino acids
cannot be synthesised and must be obtained from the diet
what are the 9 essential amino acids
If Learnt This Huge List May Prove Truly Valuable
isoleucine, lysine, threonine, histidine, leucine, methionine, phenylalanine, tryptophan, valine
what are triacylglycerols
3 fatty acids esterified to one glycerol
does fat contain more energy that carbohydrates
fats contain much less oxygen than carbohydrates or proteins so yield more energy when oxidised
3 types of triacylglycerols
- saturated (no C=C, solid at room temp)
- unsaturated (C=C, liquid at room temp)
- trans (artificially produced)
why are fats important part of diet
- absorption of fat-soluble vitamins (A,D,E,K) from gut
- energy yield 2.2x greater than carbs or proteins
- provide the essential fatty acids (linoleic and linolenic acid) which are components of cell membranes and precursors of important regulatory molecules
what do electrolytes do
establish ion gradients across membranes + maintain water balance
e.g. sodium, potassium, chloride
Minerals that are electrolytes
sodium, potassium, chloride
minerals that are cofactors for enzymes
iron, magnesium, manganese, cobalt, copper, zinc and molybdenum
vitamins and minerals that have important antioxidant properties
vitamin C, vitamin E, selenium
how are vitamins soluble
fat or water soluble
the deficiency disease associated with vitamin C is
scurvy
the deficiency disease associated with vitamin B12 is
anaemia
the deficiency disease associated with vitamin A is
xerophthalmia
the deficiency disease associated with vitamin D is
rickets
the deficiency disease associated with vitamin K is
defective blood clotting
what is recommended intake of dietary fibre
18g/day
examples of dietary fibre
cellulose, ligning, pectins, gums
how is fibre digested
it cannot be broken down by human digestive enzymes but is essential for normal functioning of GI
what is the recommended proportions of energy supply
30% from fats
55% from carbohydrate
15% from protein
why are amino acids important
- building blocks of proteins
- used in synthesis of many N-containing compounds like creatine, purines, pyrimidine and haem
what is zero nitrogen balance
nitrogen intake equals nitrogen output
positive nitrogen balance in growing children and pregnancy
negative nitrogen balance in starvation and tissue wasting diseases
what is the average daily requirement of protein
0.5g/kg body weight
how much of the body weight is water
50-60%
70% in children
50% in elderly and obese
average water loss from the body
2.5 litres/day
urine 1500ml
expired air 400ml
skin 500ml
faeces 100ml
DRVs
Dietary Reference Values
estimates of the amount of energy and nutrients needed by different groups of healthy UK population
how is body weight determined
difference between input of substances into body and output of substances and energy from the body
what do energy requirements vary depending on
age, sex, body composition, physical activity
with moderate physical activity what is the daily energy expenditure
70kg male = 12000kJ
58kg female = 9500kJ
what are the 3 components of daily energy expenditure
basal metabolic rate (BMR)
physical activity level (PAL)
diet-induced thermogenesis (DIT)
what is basal metabolic rate
energy required to maintain life at physical, digestive and emotional rest e.g. maintenance of cells, organ function and body temperature
factors affecting BMR
- body size
- gender (higher in males)
- environmental temperature (higher in cold)
- endocrine status (higher in hyperthyroidism)
- body temperature (12% increase per degree)
rough estimate of BMR
100 x weight in kg (units = kJ/24hr)
what is physical activity level
energy required by skeletal and cardiac muscle for voluntary physical activity
rough estimate of PAL
sedentary = 30 kJ/kg/day
moderate activity = 65 kJ/kg/day
very active = 100 kJ/kg/day
what is diet induced thermogenesis
energy required to digest, absorb, distribute and store the nutrients from the food we eat
rough estimate of DIT
10% of energy content of ingested food
how is body weight maintained
energy intake = energy expenditure
how is body mass index (BMI) calculated
BMI = weight (kg) / height (m^2)
what are the BMI ranges
- Underweight: <18.5
- Healthy Weight: 18.5-24.9
- Overweight: 25-29.9
- Obese: 30-34.9
- Severely obese: >35
what is an alternative measurement to BMI as a better measure of obesity and CVD risk
waist to hip ratio
what is obesity
- excessive accumulation of body fat in adipose tissue
- BMI >30
- result of energy intake exceeding energy expenditure over a period of years
what is obesity associated with an increased risk of
hypertension
heart disease
stroke
type 2 diabetes
certain cancers
gall bladder disease
osteoarthritis
greater proportion of fat in abdomen compared to hips associated with increased risk of
insulin resistance
hyperinsulinism
type 2 diabetes
hypertension
hyperlipidaemia
stroke
premature death
why is total starvation not a preferred method of weight loss
- protein metabolism increases to maintain blood glucose by gluconeogenesis so lean body mass begins to disappear
-liver starts converting fatty acids to ketone bodies to be used as fuel by CNS which disturbs blood pH and leads to dehydration
what is the eatwell guide
A food guide that shows you the types of food needed to make up a healthy diet, and the proportions of food you need
what is malnutrition
any condition caused by in-balance in what individual eats and what individual requires to maintain health (under-nutrition or over-nutrition)
what is malabsorption
failure to digest and/or absorb ingested nutrients
what is protein-energy malnutrition
covers a spectrum of conditions seen in starvation which leads to loss of subcutaneous fat and muscle wasting
e.g. marasmus and kwashiorkor
what is marasmus
- most commonly seen in children <5
- child looks emaciated with obvious signs of muscle wasting and loss of body fat
- no oedema
- thin + dry hair, diarrhoea, anaemia
what is Kwashiorkor
- occurs typically in a young child displaced from breastfeeding and fed a low protein diet
- child is apathetic, lethargic and anorexic
- generalised oedema and pitting oedema
- distended abdomen due to hepatomegaly and/or ascites
- low serum albumin and anaemia
how does kwashiorkor cause oedema
- insufficient amino acids in liver to make blood proteins like albumin
- decreases plasma oncotic pressure
- increasing net flow of fluid from capillaries to interstitium
- results in oedema
what is refeeding syndrome
hypokalemia, hypomagnesemia, and hypophosphatemia after refeeding a starved patient
how does refeeding syndrome occur
- rapid refeeding of energy rich foods in starved or inadequately nourished patients
- rapidly increases blood sugar and insulin
- results in glycogen, fat and protein synthesis
- these processes utilise phosphate, magnesium and potassium from already depleted body stores
- results in electrolyte abnormalities
what are the trace elements
copper, zinc, iodine, selenium
what are the ultratrace elements
chromium, manganese, molybdenum
electrolyte and water requirements of IV fluids
- Na+, K+, Cl- 1mmol/kg/day each
- water 30 ml/kg/day